Process for the stabilization of dusting surfaces

ABSTRACT

The invention relates to a process for the stabilization of dusting surfaces characterized in that the dusty ground is tilled or scarified and mixed with polymers in form of water-redispersible polymer powders, which are optionally re-emulsifiably modified, or reemulsifiable modified aqueous polymer dispersions, which are optionally sprayed on to the untreated dusty ground. In a preferred embodiment the redispersible polymer powder, respectively the reemulsifiable modified redispersible polymer powder or the reemulsifiable modified aqueous polymer dispersion, is combined with hydraulically setting compounds, preferably cement and/or gypsum.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. application Ser. No.11/012,647,filed Dec. 15, 2004.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a process for the stabilization of dustingsurfaces with polymers in form of water-redispersible polymer powders,which are optionally reemulsifiable modified, or reemulsifiable modifiedaqueous polymer dispersions.

2. Background Art

Dust control and soil stabilization is a major environmental and healthissue. Dust, for example road dust of unpaved roads and gravel roads,pollutes the environment and poses health risks. Soil stabilizationretards both wind and water erosion. Furthermore the condition of roadsis an important part of road safety. It is improved by the stabilizationof unpaved roads preventing the development of ruts, bumps andwashboards. Fine particle stabilization also has significant economicadvantages in extending the working lives of such machinery as airheating and cooling units and turbine engines. In general dust iscomposed of fine particles with a particle size of 1 μm to 2 mm.

For soil stabilization it has been the state of art to spray mineral oilproducts onto the surface of unpaved roads with all the environmentaldisadvantages. Water-dilatable binders like calcium chloride solutionsand lignosulfonate solutions have also been used for dust control andsurface stabilization. JP-B 05-53881, ZA-A 8803253, and JP-B 49046716concern surface stabilization with conventional aqueous polymerdispersions. Aqueous polymer solutions, e.g. solutions of polyacrylicacid have been used to control dust on gravel roads. The major problemof water based polymer products is that 1) they only bind dustingparticles a single time because they do not redisperse, 2) they are slowto dry and form films due to the water necessary to apply thedispersions and 3) they are more difficult to till or scarify into thematerial being bound due to their inherent liquid state. Therefore everyhalf year these compounds have to be applied again. When used in deepreaching applications (i.e. depths of more than one inch) to improvedurability, water based products show the additional disadvantage ofdrying much too slowly, which leads to prohibitive closure times of theroad. Considering the above mentioned rate of erosion and the subsequentfrequent rate of application, the state of the art is not onlyeconomically disadvantageous but also environmentally questionableconsidering the biodegradability and the chemical nature of most monomerbases now in use for this type of application.

U.S. Pat. No. 3,736,758 discloses a process for rendering soil atchemical storage sites impervious to liquids, by adding a conventionalpolymer dispersion to a depth of soil, moistening and compacting thesoil, and applying an impermeable thick film or coating of an organicpolymer over the treated and compacted soil to render the surfaceimpermeable. The process is expensive due to the amount of impermeablepolymer added onto the surface, and for many such polymers requires anorganic solvent which is environmentally undesirable. If the integrityof the stabilized soil is compromised, the soil cannot be againstabilized without removing the impermeable coating and addingadditional polymer dispersion.

SUMMARY OF THE INVENTION

It was thus an object of the invention to provide a process for soilstabilization of dusting surfaces which avoids environmentaldisadvantages, and which does not need a complete renewal of the surfacetreatment in short time cycles. These and other objects are achieved bya process for the stabilization of dusting surfaces, characterized inthat the dusty ground is tilled or scarified and mixed with polymers inthe form of water-redispersible polymer powders, which are optionallyreemulsifiable modified, or reemulsifiable modified aqueous polymerdispersions, which are optionally sprayed on to the untreated dustyground.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

Redispersible polymer powders are characterized in that they are readilyredispersible after stirring with water, largely breaking down into theoriginal particles of the initial dispersions, and forming waterresistant polymer films. Redispersible reemulsifiable modified polymerpowders are redispersible polymer powders that are modified by theaddition of an amount of dispersant which causes controlled partialreemulsification of the polymer film on exposure to sufficient moisture.Reemulsifiable modified polymer dispersions, in contrast to commonpolymer dispersions which build up water-resistant polymer films,contain an additional amount of dispersant which causes controlledreemulsification of the first obtained polymer film after furthercontact with water. In general, reemulsifiable modified polymer powdersor reemulsifiable modified aqueous polymer dispersions mean that apolymer film resulting from application of the polymer or polymerdispersion will begin reemulsifying (breaking down) immediately onexposure to water under normal conditions to a degree of at least 50% byweight, preferably of at least 90% by weight. The polymers are based onone or more monomers from the group consisting of vinyl esters,(meth)acrylates, vinyl aromatics, olefins, 1,3-dienes and vinyl halidesand, if required, further monomers copolymerizable therewith.

Suitable vinyl esters are those of carboxylic acids having 1 to 12 Catoms. Vinyl acetate, vinyl propionate, vinyl butyrate, vinyl2-ethylhexanoate, vinyl laureate, 1-methylvinyl acetate, vinyl pivalateand vinyl esters of α-branched monocarboxylic acids having 9 to 11 Catoms, for example VeoVa9^(R) or VeoVa10^(R) (trade names of ResolutionPerformance Products), are preferred. Vinyl acetate is particularlypreferred.

Suitable acrylate and methacrylate monomers include esters ofstraight-chain or branched alcohols having 1 to 15 carbon atoms.Preferred methacrylates or acrylates are methyl acrylate, methylmethacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate,propyl methacrylate, n-butyl acrylate, n-butyl methacrylate, tert-butylacrylate, tert-butyl methacrylate and 2-ethylhexyl acrylate. Methylacrylate, methyl methacrylate, n-butyl acrylate, tert-butyl acrylate and2-ethylhexyl acrylate are particularly preferred. Preferred vinylaromatics are styrene, methylstyrene and vinyltoluene. A preferred vinylhalide is vinyl chloride. The preferred olefins are ethylene andpropylene, and the preferred dienes are 1,3-butadiene and isoprene.

If required, 0.1 to 5% by weight, based on the total weight of thecopolymer, of auxiliary monomers may also be copolymerized. Preferably,0.5 to 2.5% by weight of auxiliary monomers is used. Examples ofauxiliary monomers are ethylenically unsaturated mono- and dicarboxylicacids, preferably acrylic acid, methacrylic acid; ethylenicallyunsaturated carboxamides and carbonitriles, preferably acrylamide andacrylonitrile; and ethylenically unsaturated sulfonic acids and theirsalts, preferably vinyl sulfonic acid and 2-acrylamido-2-methylpropanesulfonic acid. Further examples are precrosslinking co-monomers such aspolyethylenically unsaturated comonomers, for example divinyl adipate ortriallyl cyanurate, or postcrosslinking comonomers, for exampleN-methylolacrylamide (NMA), N-methylol-methacrylamide, alkyl ethers,such as the isobutoxy ether, or esters, of N-methylolacrylamide.Comonomers having epoxide functional groups, such as glycidylmethacrylate and glycidyl acrylate, are also suitable. Further examplesare comonomers having silicon functional groups, such as(meth)acryloyloxypropyltri(alkoxy)silanes, vinyltrialkoxysilanes andvinylmethyldialkoxysilanes.

The choice of monomers or the choice of the amounts by weight of thecomonomers is made in such a way that in general a glass transitiontemperature Tg of −50° C. to +50° C., preferably −30° C. to +40° C.,most preferably −5 to 15° C., results. The glass transition temperatureTg of the polymer can be determined in a known manner by means ofdifferential scanning calorimetry (DSC). The Tg can also be calculatedapproximately beforehand using the Fox equation. According to T. G. Fox,BULL. AM. PHYSICS Soc. 1, 3, page 123 (1956), the following isapplicable: 1/Tg=x₁/Tg₁+x₂/Tg₂ + . . . + x_(n)/Tg_(n), where x_(n) isthe mass fraction (% by weight/100) of the monomer n and Tg_(n) is theglass transition temperature in Kelvin of the homopolymer of the monomern. Tg values for homopolymers appear in Polymer Handbook, 2nd Edition,J. Wiley & Sons, New York (1975).

Particularly preferred are homopolymers and copolymers of vinyl estermonomers, particularly vinyl acetate. Most preferred are polyvinylacetate, copolymers of vinyl acetate and ethylene, copolymers comprisingvinyl acetate, ethylene and a vinylester(s) of a-branched monocarboxylicacids having 9 to 11 C atoms. It being possible for said polymers alsoto contain, if required, one or more of the abovementioned auxiliarymonomers.

The polymers are prepared in a manner known per se by the emulsionpolymerisation process or by the suspension polymerisation process,preferably by the emulsion polymerisation process, the polymerisationtemperature being in general 40° C. to 100° C., preferably 45° C. to 90°C. In the copolymerisation of gaseous comonomers such as ethylene,1-3-butadiene or vinyl chloride, superatmospheric pressure, in generalfrom 5 bar to 100 bar, may also be employed.

The polymerisation is initiated with the water-soluble ormonomer-soluble initiators or redox initiator combinations customarilyused for emulsion polymerisation or suspension polymerisation. In apreferred embodiment the monomers are stabilized by protective colloids.

Suitable protective colloids are polyvinyl alcohols;polyvinylpyrrolidones; polyvinyl acetals; polysaccharides inwater-soluble form, such as starches (amylose and amylopectin),celluloses and their carboxymethyl, methyl, hydroxyethyl andhydroxypropyl derivatives; proteins, such as casein or caseinate,soybean protein and gelatin; ligninsulfonates; synthetic polymers, suchas (meth)acrylic acid, copolymers of (meth)acrylates with comonomerunits having carboxyl functional groups, poly(meth)acrylamide,polyvinylsulfonic acids and their water-soluble copolymers; melamineformaldehyde sulfonates, naphthalene formaldehyde sulfonates and styrenemaleic acid and vinyl ether/maleic acid copolymers. Partially hydrolysedor completely hydrolysed polyvinyl alcohols are preferred. Theprotective colloids are generally added in a total amount of 1 to 20% byweight, based on the total weight of the monomers, during thepolymerisation.

It may be advantageous additionally to use small amounts of emulsifiersif desired, for example 1 to 5% by weight, based on the amount ofmonomers. Suitable emulsifiers are anionic, cationic and non-ionicemulsifiers, for example anionic surfactants, such as alkylsulfateshaving a chain length of 8 to 18 C atoms, alkyl or alkylaryl ethersulphates having 8 to 18 C atoms in the hydrophobic radical and up to 40ethylene oxide or propylene oxide units, alkane- or alkylarylsulfonateshaving 8 to 18 C atoms, esters and monoesters of sulfosuccinic acid withmonohydric alcohols or alkylphenols, or nonionic surfactants, such asalkyl polyglycol ethers or alkylaryl polyglycol ethers having 8 to 40oxyetehylene units therein.

The thus obtained initial polymer dispersions have a solids content of30 to 70%, and may be diluted for further processing or finalapplication. For the preparation of the water-redispersible polymerpowders, the aqueous dispersions are spray-dried after the addition ofprotective colloids as spraying assistants.

As a rule, the spraying assistant is used in a total amount of 3 to 30%by weight, based on the polymeric components of the dispersion. Thismeans that the total amount of the protective colloid before the dryingprocess should be at least 3 to 30% by weight, based on the polymerfraction; preferably, 5 to 20% by weight, based on the polymer fraction,are used. Suitable spraying assistants are partially hydrolysedpolyvinyl alcohols; polyvinylpyrrolidones; polysaccharides inwater-soluble form such as starches (amylose and amylopectin),celluloses and their carboxymethyl, methyl, hydroxyethyl andhydroxypropyl derivatives; proteins such as casein or caseinate, soybeanprotein, gelatin; ligninsulfonates; synthetic polymers such aspoly(meth)acrylic acid, copolymers of (meth)acrylates with co monomerunits having carboxyl functional groups, poly(meth)acrylamide,polyvinylsulfonic acids and their water-soluble copolymers; melamineformaldehyde sulfonates, naphthalene formaldehyde sulfonates andstyrene/maleic acid and vinyl ether-/maleic acid copolymers.

The rebuilding mechanism can be enhanced by the combination of thewater-redispersible polymer powders with dispersants, to obtainreemulsifiable modified water-redispersible polymer powders. This typeof polymer powder facilitates the redispersion of the polymer powderafter contact with water. Common dispersants are the protective colloidsand emulsifiers already mentioned above. Preferred emulsifiers are basedon ethoxylated fatty alcohols. The preferred dosage of additionaldispersant is 1 to 20% based on the total weight percent ofredispersible polymer powder used. These additional components forapplication and performance control may be added either during the stageof polymerization, the stage of spray drying or as a post add, thelatter being preferred.

In the case of the reemulsifiable modified aqueous polymer dispersions,dispersants are added after the preparation of the polymer dispersion.Common dispersants are the protective colloids and emulsifiers alreadymentioned above. Preferred emulsifiers are based on ethoxylated fattyalcohols. The preferred dosage of dispersant is 1 to 20% based on thetotal weight percent of the polymer dispersion used.

In a further preferred embodiment the redispersible polymer powder, andmore preferably the reemulsifiable modified redispersible polymer powderor the reemulsifiable modified aqueous polymer dispersion, is combinedwith hydraulically setting compounds, preferably cement and/or gypsum.With this combination an improvement of the drying time is achieved, andredispersion of compositions containing hydraulically setting compoundsis aided as well.

The process is suitable for the soil stabilisation and dust binding ofvarious undergrounds: Unpaved dirt roads, forestry roads, agriculturalaccess roads, road shoulders, road bed sub-base, construction sites,land development, slopes, and dumps, coal piles, seasonal roads, privateroads and driveways, parking lots, airstrips, athletic fields, landingpads, public parks, and athletic fields. Usually the underground istilled or scarified to a depth of 1 to 500 mm, preferably 50 to 150 mm,and the loose material is admixed with the polymer powder or the polymerdispersion. Preferably 0.01 to 5% b.w. polymer solids, particulary 0.2to 2.0% b. w. polymer solids, of polymer powder or polymer dispersion,based on the soil material to be stabilized, is used. In general, thethus prepared underground is then levelled and compacted or graded.Alternativly polymer dispersions can be sprayed onto the untreatedunderground.

For the activation of binding of the underground it only needs to beexposed to moisture, preferably by spraying with water, whereuponfilm-forming of the water-redispersible polymer powder occurs.Redispersable powders, especially with additional dispersant(s)(reemulsifiable modified), have unique performance properties superiorto the state of the art: With every rainfall, the film fibers willdesintegrate to a controlled extent allowing a refilming process tostart in the next drying cycle. Thus any newly formed dust particleswill be trapped, with film-forming occuring as deep as the waterpenetrates into the material and as deep as the polymer powder isadmixed with the loose dirt material. For these reasons, in contrast tothe soil stabilization by spraying the underground with common polymerdispersions which build strong films but without any rebinding capacity,the claimed polymer film is rebuilt again and again after contact withmoisture. Additionally dust binding occurs as deep as the dust isadmixed with polymer powder. With common aqueous polymer dispersions,binding of dust particles only occurs on the initial application andproper film formation of the polymer only occurs near the applicationsurface where sufficient drying can occur by evaporation.

In the case of reemulsifiable modified polymer dispersions, no strongwater-resistant polymer films occur as is the case with common polymerdispersions. After rainfall or after spraying with water following alonger dry period, the polymer film disintegrates and is rebuilt againand again, and additional dust binding occurs in a similar mechanism asalready described above for redispersible polymer powders.

With cementitious materials added, further improvement to the state ofthe art occurs as a result of a drying mechanism in addition toevaporation. Cementitious materials may be added in amounts of less than1% by weight to 20% by weight, preferably 1% to 10%, and most preferablyabout 1% to 4% by weight, relative to the weight of soil to be bound. Asis the case with common aqueous dispersions, proper film formation belowthe surface of an application, whether initially sprayed onto thesurface or tilled into the ground, may never occur, and then only oververy long periods of time. With the addition of cementitious materials,drying occurs below the surface via chemical consumption of the water,whether a polymer powder or an aqueous dispersion is applied, to supportproper film formation regardless of the localized evaporation rate atvarying depths.

The soil thus stabilized may, in general, be quite hard, similar uponvisual inspection in the case of sand or sandy soils, to the appearanceof cements or mortars. The soil thus stabilized also possessesconsiderable tensile strength and modulus, and depending upon the depthof soil treated and the amount of treating agent, may supportconsiderable loads. Should the upper level crack, be pulverized withheavy machinery, or have additional soil or dust deposited thereon, thesoil may be wetted and again compacted, renewing the stabilization ofthe soil. While a strongly stabilized soil is thus obtained, the soilremains permeable to water.

Because it is desirable for the soil to be able to be restabilized byaddition of moisture, whether purposefully added or as a result ofnatural precipitation, it is most desirable that the surface remain freeof impermeable films and vapor barriers, whether applied in situ, forexample by spraying a non-foaming polyurethane or other thermosetpolymer layer, or by coverage with a plastics film. Thus, the process ofthe invention preferably does not employ the addition of any waterimpermeable film, and in particular, any polymer film of sufficientintegrity and imperviousness such that a relatively uniform rewetting ofthe soil is prevented. It would not depart from the spirit of theinvention, however, to spray onto the treated area a very thin film of awater impermeable substance uniformly or over portions, wherein thethickness or the areal discontinuities or both are such that rewettingof the soil can in fact readily take place, preferably withoutscarifying or reworking of the soil. Such films are, in general, lessthan 0.1 mm in thickness, and are themselves preferably formed of anaqueous polymer dispersion, but not of a polymer which is waterredispersible. Coatings of thermoset, crosslinked polymers such aspolyurethanes, epoxy resins, vinyl ester resins, and the like are inparticular preferably avoided. Even without such coatings, a hard,stabilized soil is produced, which, in the case of use of redispersiblepolymers alone is at least somewhat water permeable, and in the casewhere cementitious ingredients are also added, is water vapourpermeable, which is not the case when films such as polyurethanes orepoxy resins are applied to the surface.

The tests below serve as a further illustration of the invention:

For the test of soil stabilization, dirt was obtained from two differentMichigan dirt roads that represent the primary target for such anapplication. The dirt collected was characterized before testing beganwith the following results: Sieve Size Percent Retained Particle SizeAnalysis of MI Dirt  16 44.4  30 15.4  50 19.1  70 7.4 100 5.2 200 4.4Pan 4.2 Physical Properties of MI Dirt Avg Water Content 3.48% Avg WetDensity 1.92 g/ml Avg Dry Density 1.79 g/mlTesting of soil stabilisation:

COMPARISON EXAMPLE 1

250 g of MI dirt was weighed into a cup.

For testing a state of art dust binding composition, 4.7 g of apolyacrylate dispersion (solids content 47%) and 9 g of water were mixedinto the dirt until uniform wet-out appeared to have been achieved. Thecup was then placed in an oven at 50° C. to accelerate drying. After 12hours the cup was removed from the oven and was subjectively evaluatedfor binding of the dust by shaking the cup and observe the mass ofparticles that is emitted.

COMPARISON EXAMPLE 2

According to comparison example 1, but instead of 4.7 g of the polymerdispersion, 15 g of water was mixed with the dust. The cup was thenplaced in an oven at 50° C. to accelerate drying. After 12 hours the cupwas removed from the oven and was subjectively evaluated for binding ofthe dust by shaking the cup and observe the mass of particles that isemitted.

EXAMPLE 3

According to comparison example 1, but instead of 4.7 g of the polymerdispersion, 5 g of a redispersible polymer powder based on a vinylacetate-ethylene copolymer was mixed with a metal spatula into the dirtuntil it seemed homogenous. Then 15 g of water was added to thehomogenous mixture and mixed in. The cup was then placed in an oven at50° C. to accelerate drying. After 12 hours the cup was removed from theoven and was subjectively evaluated for binding of the dust by shakingthe cup and observe the mass of particles that is emitted.

EXAMPLE 4

According to comparison example 1, but instead of 4.7 g of the polymerdispersion, 1.5 g of a redispersible polymer powder based on a vinylacetate-ethylene copolymer, and 3 g of cementitious material was mixedwith a metal spatula into the dirt until it seemed homogenous. Then 15 gof water was added to the homogenous mixture and mixed in. The cup wasthen placed in an oven at 50° C. to accelerate drying. After 12 hoursthe cup was removed from the oven and was subjectively evaluated forbinding of the dust by shaking the cup and observe the mass of particlesthat is emitted.

EXAMPLE 5

Unlike comparison example 1, 1000 g of MI dirt was introduced into a oneliter beaker. To the beaker was added 10 g of a redispersible polymerpowder based on a vinyl acetate-ethylene copolymer, and 2.5 g of anethoxylated fatty alcohol was mixed with a metal spatula into the dirtuntil it seemed homogenous. Then 15 g of water was added to thehomogenous mixture. The beaker was then placed in an oven at 50° C. toaccelerate drying. After 12 hours the beaker was removed from the ovenand was subjectively evaluated for binding of the dust by shaking thecup and observe the mass of particles that is emitted.

The bound layer of dirt at the top of each beaker was then removed,physically crushed to a similar particle size as the original MI dirt,was mixed with 5% by weight of the homogeneous mixture from itsrespective beaker (to simulate mixing that would occur in an actualapplication), and was added back to the beaker. 15 g of water was thenadded to the top of the beaker, and the was placed back in the oven at50° C. to accelerate drying. After 12 hours, the beaker was removed fromthe oven and was subjectively evaluate for binding of the dust byshaking the beaker and observing the mass of particles that was emitted.

EXAMPLE 6

According to example 5, but in addition to the redispersible polymerpowder and to the ethoxylated fatty alcohol 20 g of cementitiousmaterial was mixed with a metal spatula into the dirt until it seemedhomogenous. Then 15 g of water was added to the top of the beaker. Thecup was then placed in an oven at 50° C. to accelerate drying. After 12hours the cup was removed from the oven and was subjectively evaluatedfor binding of the dust by shaking the cup and observe the mass ofparticles that is emitted.

The bound layer of dirt at the top of each beaker was then removed,physically crushed to a similar particle size as the original MI dirt,was mixed with 5% by weight of the homogeneous mixture from itsrespective beaker (to simulate mixing that would occur in an actualapplication), and was added back to the beaker. 15 g of water was thenadded to the top of the beaker, and the was placed back in the oven at50° C. to accelerate drying. After 12 hours, the beaker was removed fromthe oven and was subjectively evaluate for binding of the dust byshaking the beaker and observing the mass of particles that was emitted.

Test Results:

The results were rated as follows:

-   3=Very good dust binding, better than state of the art-   2=Good dust binding, similar to the state of the art-   1=Low dust binding

0=No dust binding TABLE 1 Cycle/ Comp. Comp. Example Example ExampleComp. Sample Ex. 1 Ex. 2 3 4 5 Ex. 6 First 2 1 3 2 2.5 3 Second — — — —2.5 3

1. A process for stabilizing a soil surface, comprising treating soil bymeans of at least one of a. admixing with soil a water-redispersiblepolymer powder or reemulsifiable-modified redispersible polymer powderto form a soil/polymer mixture and wetting said soil/polymer mixture toform a polymer-bound soil; or b. applying to soil an aqueous dispersionof at least one of a water-redispersible polymer powder or areemulsifiable-modified redispersible polymer powder, and optionallycompacting the soil thus treated, with the proviso that the soil surfaceis free of water-impermeable polymer film such that the soil isrewettable with water.
 2. The process of claim 1, wherein the soilsurface is free of any water-impermeable polymer film.
 3. The process ofclaim 1, wherein the soil is sand and an aqueous dispersion of awater-redispersible polymer powder or remulsifiable-modifiedredispersible polymer powder is applied to the soil.
 4. The process ofclaim 1, wherein a water-redispersible polymer powder or areemulsifiable-modified redispersible polymer powder is admixed withsoil, and said wetting is accomplished by applying an aqueous dispersionof a water-redisperesible polymer powder and/or areemulsifiable-modified redispersible polymer powder.
 5. The process ofclaim 1, wherein a composition comprising a water-redispersible polymerpowder and a hydraulically settable cement is admixed with soil andwetted.
 6. The process of claim 1, wherein a composition comprising areemulsifiable-modified redispersible polymer powder and a hydraulicallysettable cement is admixed with soil and wetted.
 7. The process of claim1 wherein said water-redispersible polymer is a polymer prepared bycopolymerizing a monomer mixture comprising at least one monomerselected from the group consisting of vinyl esters, (meth)acrylates,vinyl aromatics, olefins, 1,3-dienes, and vinyl halides, in the presenceof a protective colloid.
 8. The process of claim 1, wherein saidwater-redispersible polymer is a polymer prepared by copolymerizing amonomer mixture comprising vinyl acetate and ethylene in the presence ofa protective colloid.
 9. The process of claim 1 wherein saidwater-redispersible polymer is a polymer prepared by copolymerizing amonomer mixture comprising at least one vinyl ester and an olefin, inthe presence of a protective colloid, and wherein a dispersant is addedto the water-redispersible polymer prior to adding saidwater-redisperesible polymer to the soil, or is added to the soil withthe water-redispersible polymer, prior to compaction of the soil. 10.The process of claim 1, wherein said water-redispersible polymer is apolymer prepared by copolymerizing a monomer mixture comprising vinylacetate and ethylene in the presence of a protective colloid, andwherein a dispersant is added to the water-redispersible polymer priorto adding said water-redisperesible polymer to the soil, or is added tothe soil with the water-redispersible polymer, prior to compaction ofthe soil.
 11. The process of claim 1, wherein the soil is compacted in amoist state.
 12. The process of claim 2, wherein the soil is compactedin a moist state.
 13. A process for restabilizing stablized soilprepared by the process of claim 1, comprising rewetting the soil. 14.The process of claim 13, wherein the soil is tilled or scarified priorto, during, or following rewetting, and is subsequently compacted.
 15. Astabilized soil, prepared by the process of claim 1, having a hardsurface permeable to water.
 16. A stabilized soil, prepared by theprocess of claim 2, having a hard surface permeable to water.
 17. Astabilized soil, prepared by the process of claim 3, having a hardsurface permeable to water.
 18. A stabilized soil, prepared by theprocess of claim 4, having a hard surface permeable to water.
 19. Astabilized soil, prepared by the process of claim 5, having a hardsurface permeable to water vapor.
 20. A stabilized soil, prepared by theprocess of claim 6, having a hard surface permeable to water vapor.